This invention relates to a measuring tool that can be used to adjust the distance between a paint applicator and an external surface of an automotive body. Proper adjustment of the paint applicator in a paint booth promotes the even (consistent) application of a paint coat onto the surface of an automotive body while the body is being conveyed through the paint booth (during initial manufacture of the automotive vehicle).
During vehicle manufacturing operations, the vehicle body is often painted in a painting booth, or tunnel, that has various rooms (or chambers) for performing various operations on the auto boy, e.g. cleaning the body surface, applying colorant and clear coat to the body surface, and drying the auto body surface to prevent one coat from flowing or merging with another coat.
Many of the painting operations are performed automatically by automatic paint spray devices stationed at different points along the tunnel, for spraying paint onto specific areas of the vehicle body while the auto body is being conveyed through the tunnel at a relatively constant slow velocity. Such paint spray devices can take the form of electrostatic sprayers having rotary spray heads (or spray bells), as shown e.g. in U.S. Pat. No. 5,353,995 issued to P. Chabert. The paint can be supplied to the individual sprayers as a pressurized fluidized power.
The sprayers can be arranged in banks alongside the path taken by the vehicle body. U.S. Pat. No. 3,709,190 to H. Von Gottberg et al and U.S. Pat. No. 5,427,619 to P. Ehinger show some sprayer arrangements that can be used to obtain complete coating coverage of a vehicle body.
For optimum performance, each spray device should be spaced from the vehicle surface by a predetermined distance, e.g. eight or nine inches. The optimum spacing can vary from one sprayer size (or sprayed material) to another sprayer size (or material). If the sprayer head is too close to the auto body surface the coating may discolor due to burning associated with excessively high voltages. If the sprayer head is too far away from the auto body the coating can be excessively light or uneven.
In some situations the spray device can be mounted in a stationary position along the path taken by the auto body. In other situations, the spray device is movable in a direction transverse to the auto body path, in order to keep the spray device at a constant distance from the contoured auto body surface while the surface is moving incrementally toward or away from the spray device. In either situation load forces associated with operation of the spray devices can cause the spray devices to lose its adjustment; an individual spray device can shift toward or away from the path of the auto body surface, so that the quality of the paint coating on the auto body surface is degraded.
Typically, upwards of twenty five paint spray devices are required to provide complete coverage of an auto body. Should any one of the spray devices shift out of adjustment the entire auto body painting operation may be adversely affected, requiring a repainting operation. Therefore, it is necessary that all paint spray devices in the system be in proper adjustment.
The present invention relates to a low cost simplified tool that can used for readily adjusting the distance between a paint spray head (or bell) and an auto body surface. Preferably the tool is adjustable so that it can be used for setting a spray head at different distances from an auto body surface, in accordance with various different optimum distances that might be required in different situations. In one particular tool construction, the tool can be adjusted in one half inch increments to set the spray head-auto body surface spacing in a range from eight inch to ten inch. The same tool construction can be used for adjusting various different spray devices in the paint spray system.
The tool of the present invention can include a deflectable probe extending though a mounting fixture, so that when the fixture is temporarily placed on a paint applicator (spray device) the probe extends a predetermined distance from the applicator (i.e. the same distance as the optimum spray head-auto body surface spacing for the paint applicator). The probe is adjustable on the mounting fixture, whereby the probe can extend different distances from the paint applicator, depending on the adjusted position of the probe on the fixture.
Adjustment or testing of the paint sprayxe2x80x94auto body surface spacings is carried out when the painting tunnel is inactive, i.e. not being used for painting vehicles. The testing operations can be performed at predetermined intervals (e.g. monthly) or when the quality of the painting operation suggests that one or more of the spray devices has a shifted out of adjustment, i.e. when the spray head-auto body surface spacing is not optimum.
In usage of the measuring tool, one measuring tool is installed on each paint spray applicator in the system. For example, in a system using thirty paint applicators, a measuring tool will be installed on each paint applicator, so that all thirty paint applicators can be tested on one pass of the auto body through the tunnel. Each deflectable probe has a free end, or tip, that represents the expected location of an auto body surface when the surface is aligned with the respective paint applicator in the paint booth.
A representative vehicle body is moved through the tunnel (on the usual conveyor) so that the vehicle body takes the same path it would take during an actual painting cycle. No powder is supplied to the paint applicators during the test. Instead, one or more technicians view the various probes while the auto body is in variouspositions that it would have during actual paint spray operating periods.
Each probe is viewed with respect to the location of the probe tip in relation to the associated surface of the auto body. If a particular probe is in a deflected condition, (due to oblique contact with the auto body surface), this is an indication that the spacing between the paint applicator and the auto body surface is less than it should be. If a free space is observed between the tip of the probe and the surface of the auto body, this is an indication that the spacing between the paint applicator and the auto body is greater than it should be.
With the probes still installed on the paint applicators, the spray heads (or applicators) are adjusted so that the tips of the probes are in contact with associated surfaces on the auto body, without any probe deflection. The testing and adjusting operations are carried out with the vehicle body in various stand-still locations, corresponding to the positions that the body would have while going through an actual painting cycle.
The measuring tool herein proposed, is advantageous in that it can be used to make accurate and consistent measurements. Also, the measuring tool can remain on the paint applicator while the applicator is being adjusted, so that the magnitude of the adjustment corresponds precisely to the inaccuracy measured by the tool. The tool is costxe2x80x94effective because the tool can be installed and operated by a single person.
Specific features of the invention will be apparent from the attached drawings and description of an illustrative tool embodying the invention.